Minerals from the deep-sea are potential sources of metals such as Cu, Ni, Co, Mn, Fe, that could be mined in future by developing suitable technologies for mining as well as extracting metals from them. Several groups of environment scientists and mining engineers have been conducting studies for working out these minerals. These studies have revealed unknown physical, chemical, biological and geological conditions under which the mining system will have to operate, and also the potential impacts that may occur. The data generated through environmental studies would be useful not only in understanding the potential effects of large scale mining in marine ecosystem, but also in the development of various mining subsystems. However, owing to the uncertainty of the design of mining system and the difference in the scale of mining compared to the experiments conducted, many questions remain unanswered, which need to be considered in future.